What is this nonsense about hurting the "rare" turbo coupe cars? My god, there's more of them on the road than the "sport" V8 cars.
The 87-88 Turbocoupe is one of the best options for a V8 swap. Why?
ABS, 16" wheels, larger front brakes, DISC rear brakes, 8.8 Axle, better gears for a V8 (this compared to an XR7, or a "sport" Tbird of the same vintage).
However, you can get most of the same advantages, with even less work, with an 88-92 Mark VII LSC. You get 5 lug, you get 5.0 HO, already installed, and even larger rear brakes. Just throw in a 5 speed, and it's ready to go to town!
1987 Cougar XR7 - Powerdyne Supercharged 306, 5 speed, tons of mods 390 RWHP, 425 RWTQ.
1991 Crown Victoria, Police Interceptor - 460 Big Block, C6 Automatic.